Modern ovens are often equipped with the capability to self clean. Self-cleaning is accomplished by heating the oven to temperatures of approximately 400°–480° C. (750°–900° F.) Typically, an oven can be placed in a self cleaning mode only when the oven door is it its latched state and often a lock is provided to lock the oven in its latched state while self cleaning. Generally, most non-self cleaning or normal baking occurs at temperatures at or below 500° F. while the oven door is in either a latched or an unlatched state. Therefore the prior art has included an oven door locking mechanism, effective when the oven door is latched, which locks the oven door at a temperature around approximately 500° F.
Prior art oven door locking mechanisms take various forms. Some are manual locking devices while others are automatic or motor driven locking devices. Manual devices have been developed to include thermostatically controlled locking mechanisms to prevent the inadvertent opening of the oven door at elevated temperatures during operation. In some self cleaning ovens, the locking device uses a bimetallic coil to thermally respond to changing temperatures to effect the locked and unlocked states. Such devices are disclosed in U.S. Pat. Nos. 3,438,666; 4,133,337 and 4,838,586. However, these mechanisms are problematic as they may lock at a temperature consistent with normal baking, or unlock, allowing the oven door to be opened, while the oven cavity is dangerously hot. Such devices, if unlocked while cleaning, may pose a safety risk to persons opening the oven door. Furthermore, in a normal baking mode, if such an oven door becomes locked, it prevents the inspection of or addition to the baking foods thus leading to the possibility of overcooked or even burnt foods.
U.S. Pat. No. 5,456,243 teaches a manual oven locking device which locks and unlocks the oven door by counterbalancing springs. However, the control of temperature is limited as the spring must be changed to alter the temperature at which the oven locks or unlocks.
Hence, a problem exists in that during an extended baking cycle or a self cleaning mode, the latched oven door may become locked at ‘too low’ a temperature presenting a potential baking catastrophe or may be opened at ‘too high’ a temperature presenting a potential safety hazard.